[thereforegrin]

if he actually was, then it's not a personal attack but stating facts about a person - there's a meaningful difference.

A personal attack has no informational value (about the accused), while bringing to light bad qualities of a person does - especially if those qualities are related to the issue at hand, which in this particular situation seems to be the case.

Again, the distinction between a personal attack and proper characterisation of bad qualities rests on actual facts i.e. was it slander or was he really a bad manager?

I don't know but I personally give less probability to the former than the latter.